基于杏仁核神经元的投射靶区研究慢性应激引发焦虑障碍的机制

Chronic stress is among the most common socio-environmental factors leading to the development of anxiety disorders. Prolonged activation of basal amygdala represents one of the key mechanisms underlying the adversity of chronic stress on emotion. Recent studies have consistently shown that although the BA projection neurons (PNs) are spatially intermingled, they have clearly different projection sites and physiological function. How chronic stress recruits these functionally diverse BA PNs to cause anxiety disorders remains unclear. Our preliminary data show that the BA PNs projecting to medial prefrontal cortex (desiganeted as BA-mPFC PNs) are nearly non-overlapping with the subcortical areas such as ventral hippocampus and striatum (as non-BA-mPFC PNs). Acute restraint stress causes temporary increase of c-Fos expression in the above two PN populations. However, chronic stress causes sustained activation of non-BA-mPFC PNs but not their BA-mPFC counterparts. We hypothesize such a projection-specific recruitment of BA PNs may contribute to the development of anxiogesis by chronic stress. In this project, we attempt to investigate the time-dependence of differential activation of BA PNs by chronic stress and its underlying molecular and electrophysiological mechanisms. We will also explore the exact projection sites of the non-BA-PNs persistently activated by CIS and the functional significance of projection-specific recruitment of BA PNs in anxiogesis by chronic stress. This project will help to clarify the mechanisms underlying anxiety disorders by chronic stress based on the projection sites of individual amygdala PNs and provide mechanistic insights into the prevention and treatment of anxiety disorders.

慢性应激暴露引发焦虑障碍等多种精神疾患，而大脑杏仁核基底区（basal amygdala, BA）持续性激活在其中发挥重要作用。近年的研究表明，BA内交互混杂的投射神经元有着显著不同的支配靶区和生理功能，但慢性应激如何调控这些功能各异的神经元进而引发焦虑障碍尚不明确。预实验发现，在小鼠BA内，投射至皮层下区域的神经元极少与投射至前额叶皮层的神经元重叠；急性束缚应激引起上述两群神经元活动一过性升高，而慢性应激则导致前者（而非后者）的活动持续升高。据此推测，慢性应激可能通过差异化激活杏仁核神经元而引发异常焦虑。本项目拟研究慢性应激差异化激活BA神经元的时间积累效应及分子与电生理学机制；阐明在慢性应激过程中持续激活BA神经元的确切投射靶区；探讨神经元差异化激活在慢性应激引发异常焦虑中的功能意义，以期基于杏仁核神经元自身的投射靶区明晰慢性应激引发焦虑障碍的机制，为防治相关疾患提供新的思路。

慢性应激暴露是促进焦虑障碍等多种精神疾患发生发展的重要环境因素，应激引起大脑杏仁核基底外侧区（basolateral amygdala, BLA）持续性激活在其中发挥重要作用。有趣的是，BLA内的不同投射神经元（projection neuron, PN）个体虽然在空间分布上交互混杂，但却有着显著不同的投射靶区和生理功能。在本项目中，我们系统探讨了慢性应激对这些功能各异PN的活动调控以及相应的电生理机制，并探讨了潜在的病理意义。结果发现：1）慢性束缚应激（CRS）对BLA内不同PN个体的c-Fos表达产生了截然不同的调控：即对投射至dmPFC的PN（BLA→dmPFC PN）c-Fos表达无明显影响，却持久性上调了BLA内不投射至dmPFC PN（BLA↛dmPFC PN）上的c-Fos表达水平；2）慢性不可预见应激对上述两群神经元的c-Fos表达同样产生了不同的影响，提示这种差异化性调控在不同应激模式中具有普适性；3）糖皮质激素受体（GR）阻滞剂美非司酮可以有效阻断上述效应，表明慢性应激对BLA PN活动的差异化调控与GR激活密切相关；4）CRS对上述两群神经元的放电活动同样产生了差异化调控：即显著提升了BLA↛dmPFC PN（而非BLA→dmPFC PN）的兴奋性；5）CRS对BLA PN兴奋性的差异化调控缘于CRS显著弱化了BLA↛dmPFC PN上小电导钙激活钾离子（SK2）通道的功能，但对BLA→dmPFC PN上SK2通道无明显影响；6）被CRS调控的BLA PN主要投射到腹侧海马区（BLA→vHPC PN）而非伏隔核区；7）在BLA→vHPC PN过表达SK2通道可防止慢性应激引发的过度焦虑行为。上述研究为明晰慢性应激引发过度焦虑的杏仁核环路机制提供了重要的实验证据，并为精准干预应激的情感损伤效应提供了潜在的靶标。